SEGMENT REPORTING (Details)	3 Months Ended		9 Months Ended
	Sep. 30, 2016 USD ($)	Sep. 30, 2015 USD ($)	Sep. 30, 2016 USD ($) segment	Sep. 30, 2015 USD ($)	Dec. 31, 2015 USD ($)
SEGMENT REPORTING
Number of reportable segments | segment			3
Interest income	$ 60,284,000	$ 63,013,000	$ 175,650,000	$ 178,635,000
Interest expense	(30,685,000)	(29,535,000)	(88,622,000)	(83,846,000)
Net interest income	29,599,000	33,478,000	87,028,000	94,789,000
Provision for loan losses	0	(150,000)	(300,000)	(450,000)
Net interest income after provision for loan losses	29,599,000	33,328,000	86,728,000	94,339,000
Operating lease income	19,466,000	20,671,000	57,845,000	60,207,000
Tenant recoveries	1,185,000	2,847,000	3,844,000	7,883,000
Sale of loans, net	19,640,000	15,165,000	30,265,000	59,717,000
Realized gain on securities	7,126,000	513,000	9,524,000	23,680,000
Unrealized gain (loss) on Agency interest-only securities	(47,000)	731,000	29,000	(639,000)
Realized gain on sale of real estate, net	4,649,000	6,406,000	15,616,000	21,347,000
Fee and other income	8,101,000	3,483,000	17,258,000	10,857,000
Net result from derivative transactions	9,356,000	(42,242,000)	(66,148,000)	(54,594,000)
Earnings (loss) from investment in unconsolidated joint ventures	(141,000)	(25,000)	485,000	580,000
Gain on extinguishment of debt	0	0	5,382,000	0
Total other income (loss)	69,335,000	7,549,000	74,100,000	129,038,000
Salaries and employee benefits	(17,296,000)	(17,628,000)	(43,343,000)	(47,333,000)
Operating expenses	(4,391,000)	(4,951,000)	(15,399,000)	(20,487,000)
Real estate operating expenses	(7,969,000)	(8,975,000)	(22,613,000)	(27,976,000)
Real estate acquisition costs	(423,000)	(470,000)	(631,000)	(1,524,000)
Fee expense	(803,000)	(675,000)	(2,407,000)	(3,260,000)
Depreciation and amortization	(9,733,000)	(9,561,000)	(28,789,000)	(29,238,000)
Total costs and expenses	(40,615,000)	(42,260,000)	(113,182,000)	(129,818,000)
Tax (expense) benefit	(8,721,000)	4,181,000	(5,547,000)	(4,101,000)
Net income (loss)	49,598,000	2,798,000	42,099,000	89,458,000
Total assets	6,215,816,000		6,215,816,000		$ 5,895,212,000
Investment in unconsolidated joint ventures	33,860,000		33,860,000		33,797,000
Investment in FHLB stock	77,915,000		77,915,000		77,915,000
Senior Unsecured Notes | Various Dates
SEGMENT REPORTING
Senior Notes	559,274,000		559,274,000
LCRIP I
SEGMENT REPORTING
Fee and other income	0	0	6,905	77,447
Earnings (loss) from investment in unconsolidated joint ventures	0	0	892,000	116,000
Investment in unconsolidated joint ventures	0		0		49,000
Operating Segment | Real Estate Joint Ventures
SEGMENT REPORTING
Investment in unconsolidated joint ventures	33,900,000		33,900,000		33,700,000
Operating Segment | Loans
SEGMENT REPORTING
Interest income	40,639,000	45,195,000	117,516,000	120,932,000
Interest expense	(6,281,000)	(6,749,000)	(17,560,000)	(17,509,000)
Net interest income	34,358,000	38,446,000	99,956,000	103,423,000
Provision for loan losses	0	(150,000)	(300,000)	(450,000)
Net interest income after provision for loan losses	34,358,000	38,296,000	99,656,000	102,973,000
Operating lease income	0	0	0	0
Tenant recoveries	0	0	0	0
Sale of loans, net	19,640,000	15,165,000	30,265,000	59,717,000
Realized gain on securities	0	0	0	0
Unrealized gain (loss) on Agency interest-only securities	0	0	0	0
Realized gain on sale of real estate, net	0	519,000	0	1,771,000
Fee and other income	2,230,000	905,000	6,473,000	3,990,000
Net result from derivative transactions	4,656,000	(13,159,000)	(21,139,000)	(18,335,000)
Earnings (loss) from investment in unconsolidated joint ventures	0	0	0	0
Gain on extinguishment of debt			0
Total other income (loss)	26,526,000	3,430,000	15,599,000	47,143,000
Salaries and employee benefits	(3,300,000)	(4,525,000)	(6,300,000)	(11,436,000)
Operating expenses	0	132,000	0	301,000
Real estate operating expenses	0	0	0	0
Real estate acquisition costs	0	0	0	0
Fee expense	(1,077,000)	156,000	(1,501,000)	(1,642,000)
Depreciation and amortization	0	0	0	0
Total costs and expenses	(4,377,000)	(4,237,000)	(7,801,000)	(12,777,000)
Tax (expense) benefit	0	0	0	0
Net income (loss)	56,507,000	37,489,000	107,454,000	137,339,000
Total assets	2,427,221,000		2,427,221,000		2,310,409,000
Operating Segment | Securities
SEGMENT REPORTING
Interest income	19,630,000	17,811,000	58,088,000	57,659,000
Interest expense	(2,902,000)	(1,753,000)	(7,039,000)	(5,512,000)
Net interest income	16,728,000	16,058,000	51,049,000	52,147,000
Provision for loan losses	0	0	0	0
Net interest income after provision for loan losses	16,728,000	16,058,000	51,049,000	52,147,000
Operating lease income	0	0	0	0
Tenant recoveries	0	0	0	0
Sale of loans, net	0	0	0	0
Realized gain on securities	7,126,000	513,000	9,524,000	23,680,000
Unrealized gain (loss) on Agency interest-only securities	(47,000)	731,000	29,000	(639,000)
Realized gain on sale of real estate, net	0	0	0	0
Fee and other income	0	230,000	0	230,000
Net result from derivative transactions	4,700,000	(29,083,000)	(45,009,000)	(36,259,000)
Earnings (loss) from investment in unconsolidated joint ventures	0	0	0	0
Gain on extinguishment of debt			0
Total other income (loss)	11,779,000	(27,609,000)	(35,456,000)	(12,988,000)
Salaries and employee benefits	0	0	0	0
Operating expenses	0	0	0	0
Real estate operating expenses	0	0	0	0
Real estate acquisition costs	0	0	0	0
Fee expense	(15,000)	(10,000)	(33,000)	(31,000)
Depreciation and amortization	0	0	0	0
Total costs and expenses	(15,000)	(10,000)	(33,000)	(31,000)
Tax (expense) benefit	0	0	0	0
Net income (loss)	28,492,000	(11,561,000)	15,560,000	39,128,000
Total assets	2,650,959,000		2,650,959,000		2,407,217,000
Operating Segment | Real Estate
SEGMENT REPORTING
Interest income	4,000	0	5,000	0
Interest expense	(6,276,000)	(6,365,000)	(18,675,000)	(17,670,000)
Net interest income	(6,272,000)	(6,365,000)	(18,670,000)	(17,670,000)
Provision for loan losses	0	0	0	0
Net interest income after provision for loan losses	(6,272,000)	(6,365,000)	(18,670,000)	(17,670,000)
Operating lease income	19,466,000	20,671,000	57,845,000	60,207,000
Tenant recoveries	1,185,000	2,847,000	3,844,000	7,883,000
Sale of loans, net	0	0	0	0
Realized gain on securities	0	0	0	0
Unrealized gain (loss) on Agency interest-only securities	0	0	0	0
Realized gain on sale of real estate, net	4,649,000	5,887,000	15,616,000	19,576,000
Fee and other income	1,867,000	6,000	5,129,000	33,000
Net result from derivative transactions	0	0	0	0
Earnings (loss) from investment in unconsolidated joint ventures	(141,000)	(25,000)	(407,000)	464,000
Gain on extinguishment of debt			0
Total other income (loss)	27,026,000	29,386,000	82,027,000	88,163,000
Salaries and employee benefits	0	0	0	0
Operating expenses	0	(17,000)	(1,000)	(16,000)
Real estate operating expenses	(7,969,000)	(8,975,000)	(22,613,000)	(27,976,000)
Real estate acquisition costs	(423,000)	(470,000)	(631,000)	(1,524,000)
Fee expense	(151,000)	(123,000)	(389,000)	(230,000)
Depreciation and amortization	(9,705,000)	(9,533,000)	(28,704,000)	(29,158,000)
Total costs and expenses	(18,248,000)	(19,118,000)	(52,338,000)	(58,904,000)
Tax (expense) benefit	0	0	0	0
Net income (loss)	2,506,000	3,903,000	11,019,000	11,589,000
Total assets	859,453,000		859,453,000		868,528,000
Corporate/Other
SEGMENT REPORTING
Interest income	11,000	7,000	41,000	44,000
Interest expense	(15,226,000)	(14,668,000)	(45,348,000)	(43,155,000)
Net interest income	(15,215,000)	(14,661,000)	(45,307,000)	(43,111,000)
Provision for loan losses	0	0	0	0
Net interest income after provision for loan losses	(15,215,000)	(14,661,000)	(45,307,000)	(43,111,000)
Operating lease income	0	0	0	0
Tenant recoveries	0	0	0	0
Sale of loans, net	0	0	0	0
Realized gain on securities	0	0	0	0
Unrealized gain (loss) on Agency interest-only securities	0	0	0	0
Realized gain on sale of real estate, net	0	0	0	0
Fee and other income	4,004,000	2,342,000	5,656,000	6,604,000
Net result from derivative transactions	0	0	0	0
Earnings (loss) from investment in unconsolidated joint ventures	0	0	892,000	116,000
Gain on extinguishment of debt			5,382,000
Total other income (loss)	4,004,000	2,342,000	11,930,000	6,720,000
Salaries and employee benefits	(13,996,000)	(13,103,000)	(37,043,000)	(35,897,000)
Operating expenses	(4,391,000)	(5,066,000)	(15,398,000)	(20,772,000)
Real estate operating expenses	0	0	0	0
Real estate acquisition costs	0	0	0	0
Fee expense	440,000	(698,000)	(484,000)	(1,357,000)
Depreciation and amortization	(28,000)	(28,000)	(85,000)	(80,000)
Total costs and expenses	(17,975,000)	(18,895,000)	(53,010,000)	(58,106,000)
Tax (expense) benefit	(8,721,000)	4,181,000	(5,547,000)	(4,101,000)
Net income (loss)	(37,907,000)	$ (27,033,000)	(91,934,000)	$ (98,598,000)
Total assets	278,183,000		278,183,000		309,058,000
Investment in FHLB stock	77,900,000		77,900,000		77,900,000
Deferred tax assets	9,800,000		9,800,000		5,000,000
Corporate/Other | Senior Unsecured Notes | Various Dates
SEGMENT REPORTING
Senior Notes	$ 559,300,000		$ 559,300,000		612,600,000
Corporate/Other | LCRIP I
SEGMENT REPORTING
Investment in unconsolidated joint ventures					$ 48,771